The ongoing objectives of the immunological-toxicology group include the following interrelated efforts: (1) to evaluate and examine the influence of selected environmental chemicals on the immune response including cellular changes associated with chemical interactions in lymphoreticular cells; (2) to relate alterations in immunological functions with both general toxicity as well as specific organ toxicity; (3) to relate changes in immunological functions with altered host resistance following challenge with either syngeneic tumor cells or infectious agents employing a defined panel of infectivity models; and (4) to refine and validate a panel of immune and host resistance procedures in order to better define immunotoxicity and correlate changes in immune function with altered host resistance. Studies were performed in the following areas: (a) Attempts to elucidate the mechanisms of antibody suppression by antifolates (methotrexate and trimetrexate) and restoration with hypoxanthine. (b) Role of altered arachidonic acid metabolism in immunotoxicity of benzidine and other co-oxidative substrates. (c) Investigation into the modulation of B bell differentiation by TCDD and the identification of specific antagonists. (d) Immunotoxicity studies with methyl isocyante. (e) Development of model systems to study neutrophil function following exposure to chemical xenobiotics.